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Annotation of rpl/lapack/lapack/dlasdt.f, revision 1.6

1.1       bertrand    1:       SUBROUTINE DLASDT( N, LVL, ND, INODE, NDIML, NDIMR, MSUB )
                      2: *
1.5       bertrand    3: *  -- LAPACK auxiliary routine (version 3.2.2) --
1.1       bertrand    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                      5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.5       bertrand    6: *     June 2010
1.1       bertrand    7: *
                      8: *     .. Scalar Arguments ..
                      9:       INTEGER            LVL, MSUB, N, ND
                     10: *     ..
                     11: *     .. Array Arguments ..
                     12:       INTEGER            INODE( * ), NDIML( * ), NDIMR( * )
                     13: *     ..
                     14: *
                     15: *  Purpose
                     16: *  =======
                     17: *
                     18: *  DLASDT creates a tree of subproblems for bidiagonal divide and
                     19: *  conquer.
                     20: *
                     21: *  Arguments
                     22: *  =========
                     23: *
                     24: *   N      (input) INTEGER
                     25: *          On entry, the number of diagonal elements of the
                     26: *          bidiagonal matrix.
                     27: *
                     28: *   LVL    (output) INTEGER
                     29: *          On exit, the number of levels on the computation tree.
                     30: *
                     31: *   ND     (output) INTEGER
                     32: *          On exit, the number of nodes on the tree.
                     33: *
                     34: *   INODE  (output) INTEGER array, dimension ( N )
                     35: *          On exit, centers of subproblems.
                     36: *
                     37: *   NDIML  (output) INTEGER array, dimension ( N )
                     38: *          On exit, row dimensions of left children.
                     39: *
                     40: *   NDIMR  (output) INTEGER array, dimension ( N )
                     41: *          On exit, row dimensions of right children.
                     42: *
1.5       bertrand   43: *   MSUB   (input) INTEGER
1.1       bertrand   44: *          On entry, the maximum row dimension each subproblem at the
                     45: *          bottom of the tree can be of.
                     46: *
                     47: *  Further Details
                     48: *  ===============
                     49: *
                     50: *  Based on contributions by
                     51: *     Ming Gu and Huan Ren, Computer Science Division, University of
                     52: *     California at Berkeley, USA
                     53: *
                     54: *  =====================================================================
                     55: *
                     56: *     .. Parameters ..
                     57:       DOUBLE PRECISION   TWO
                     58:       PARAMETER          ( TWO = 2.0D+0 )
                     59: *     ..
                     60: *     .. Local Scalars ..
                     61:       INTEGER            I, IL, IR, LLST, MAXN, NCRNT, NLVL
                     62:       DOUBLE PRECISION   TEMP
                     63: *     ..
                     64: *     .. Intrinsic Functions ..
                     65:       INTRINSIC          DBLE, INT, LOG, MAX
                     66: *     ..
                     67: *     .. Executable Statements ..
                     68: *
                     69: *     Find the number of levels on the tree.
                     70: *
                     71:       MAXN = MAX( 1, N )
                     72:       TEMP = LOG( DBLE( MAXN ) / DBLE( MSUB+1 ) ) / LOG( TWO )
                     73:       LVL = INT( TEMP ) + 1
                     74: *
                     75:       I = N / 2
                     76:       INODE( 1 ) = I + 1
                     77:       NDIML( 1 ) = I
                     78:       NDIMR( 1 ) = N - I - 1
                     79:       IL = 0
                     80:       IR = 1
                     81:       LLST = 1
                     82:       DO 20 NLVL = 1, LVL - 1
                     83: *
                     84: *        Constructing the tree at (NLVL+1)-st level. The number of
                     85: *        nodes created on this level is LLST * 2.
                     86: *
                     87:          DO 10 I = 0, LLST - 1
                     88:             IL = IL + 2
                     89:             IR = IR + 2
                     90:             NCRNT = LLST + I
                     91:             NDIML( IL ) = NDIML( NCRNT ) / 2
                     92:             NDIMR( IL ) = NDIML( NCRNT ) - NDIML( IL ) - 1
                     93:             INODE( IL ) = INODE( NCRNT ) - NDIMR( IL ) - 1
                     94:             NDIML( IR ) = NDIMR( NCRNT ) / 2
                     95:             NDIMR( IR ) = NDIMR( NCRNT ) - NDIML( IR ) - 1
                     96:             INODE( IR ) = INODE( NCRNT ) + NDIML( IR ) + 1
                     97:    10    CONTINUE
                     98:          LLST = LLST*2
                     99:    20 CONTINUE
                    100:       ND = LLST*2 - 1
                    101: *
                    102:       RETURN
                    103: *
                    104: *     End of DLASDT
                    105: *
                    106:       END